Information networks are well known in the art and function to transmit information such as computer data between various computer systems operably coupled to the information network. Generally there are two types of information networks—circuit switched and packet switched. Circuit switched networks operate by creating, maintaining and transmitting data over a circuit between two network nodes. This circuit typically has a fixed bandwidth which poses some disadvantages where the amount of data is large relative to the link's bandwidth, as it may take a long time for all of the data to be transmitted. Optical Transport Networks (which will be referred to as “OTN” or “OTNs” herein) are one example of circuit-switched networks.
Multiprotocol label switching (MPLS) is a packet switching technology which directs and carries data from one network node to the next node. The multiprotocol label switching mechanism assigns labels to data packets. Packet forwarding decisions from one node to the next node are made solely on the contents of the label for each data packet, without the need to examine the data packet itself.
Generalized Multiprotocol Label Switching (GMPLS) is a type of protocol which extends MPLS to encompass network schemes based upon time-division multiplexing (e.g. SONET/SDH, PDH, G.709), wavelength multiplexing, and spatial multiplexing (e.g. incoming port or fiber to outgoing port or fiber). Multiplexing, such as time-division multiplexing is when two or more signals or bit flows are transferred over the same link. In particular, time-division multiplexing (TDM) is a type of digital multiplexing in which two or more signals or bit flows are transferred simultaneously as sub-channels in one OTN communication link, but are physically taking turns on the communication link. The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. After the last sub-channel, the cycle starts all over again. Time-division multiplexing is commonly used for OTN circuit mode communication with a fixed number of links and constant bandwidth per link. Time-division multiplexing differs from statistical multiplexing, such as packet switching, in that the timeslots are serviced in a fixed order and pre-allocated to the links.
The Optical Transport Hierarchy (OTH) supports the operation and management aspects of OTNs of various architectures, e.g., point-to-point, ring and mesh architectures. One part of the optical transport hierarchy is a multiplex hierarchy, which is a hierarchy consisting of an ordered sequence of tandem digital multiplexers that produce signals of successively higher data rates at each level of the hierarchy.
Shown in FIG. 1 is an exemplary multiplexing hierarchy specified by way of optical channel data units, i.e., ODUj, where j varies from 0 to 4; and optical channel transport units, i.e., OTUk, where k varies from 1 to 4. The optical channel data units refer to a frame format for transmitting data which can be either fixed in the amount of data and data rate or have an arbitrary data rate set by a user. Examples of optical channel data units that are fixed in the amount of data and data rate include those specified by ODU0, ODU1, ODU2, ODU3, and ODU4. One or more low order ODU containers can be multiplexed into a higher order ODU container. An example of a recently developed optical channel data unit that has an arbitrary data rate is referred to in the art as ODUflex. ODUflex containers can be sized to fit the client's bit rate thereby maximizing available bandwidth usage. Optical channel data units may hereinafter be referred to as ODUs, ODU containers, ODUj containers.
Other OTN traffic management developments are Virtual Concatenation (VCAT) and link capacity adjustment scheme (LCAS) protocol, both of which allow more efficient use of existing fixed-bandwidth circuits associated with circuit-switched OTN infrastructures. For example, these protocols are utilized in transmission of ethernet over OTN data traffic within networks, and in numerous other data transmission applications. The VCAT and LCAS protocols are described in greater detail in, for example, ITU-T standards documents G.7043 and G.7042, respectively, which are incorporated herein by reference in their entirety.
VCAT is an inverse multiplexing technique, which generally creates a large capacity payload container by distributing the client signal bits over multiple lower capacity signals which are time division multiplexed onto common transmission facilities whenever such multiplexing is possible. This allows a given source node of a network to form a virtually-concatenated group (VCG) which includes multiple members each associated with a corresponding data stream. The different data streams may then be transmitted over diverse routes through the OTN from a source node to a destination node. The destination node recombines the streams to reconstruct the original data stream injected by the source.
One example of packet-switched network for Local Area Networks (LAN or LANs) is defined by the IEEE 802 standards. These standards have found widespread acceptability and many LANs conform to these standards. A popular variation on one of the IEEE standards, IEEE Std. 802.3, 2000 Edition, is known as “Ethernet.” Traditional ethernet, as per the 802.3 standard, is a LAN utilizing a linear serial bus and uses a scheme for managing the LAN known as Carrier Sense Multiple Access with Collision Detection (“CSMA/CD”). CSMA/CD ensures that two computers transmitting at the same time detect collisions caused by simultaneous transmission, subsequently retransmit any packets which were corrupted by the simultaneous transmission during the previous transmission attempt.
The Institute of Electrical and Electronic Engineers (IEEE) 802.3ad standard defines a link aggregation Control Protocol (LACP) for use by the control process within each device employing link aggregation to verify configurations and to send packets through each of the communication links within the aggregated logical link. The standard also provides mechanisms for adding and removing ethernet links from the aggregated logical link. The IEEE 802.3ad standard works at a variety of speeds. Particularly, the IEEE 802.3ad standard applies to 10 M, 100 M, and 1000 M bit/second speeds and aggregated links can be formed using any of these physical ethernet interfaces as LAG members. The LAG members are of the same speed.
Link aggregation (LAG) is a conventional technique for aggregating standard ethernet links. The same technique can be applied to transporting packet traffic over a collection of circuits within the OTN network. An advantage of LAG is that it provides more bandwidth than a single communication link and it provides some redundancy in the case of the failure of one or more of the participating communication links. For example, a user could set up four 100 M bit/second links running in parallel between two nodes, but both nodes would handle the traffic as if there were a single 400 M bit/second link between them. In a typical implementation of LAG, the node performs a look-up on the packet header and then forwards packets to the processor which is responsible for distributing the offered traffic among the LAG members; this processor parses the packet headers to identify sub-flows and then directs each sub-flow into one of the LAG members, in a deterministic fashion. However, a major disadvantage is that the traffic distribution mechanism of LAG is based on static classification rules (based on combination of fields contained in data packets). Such rules have no knowledge of the actual bandwidth requirements of the packet flows. As a result, the performance of a LAG implementation is sensitive to the actual data flowing through the LAG, and becomes inefficient at data rates in excess of 1 Gbit/sec. At these data rates, link aggregation may result in uneven spread of the packets over the available communication links. This can result in under-utilizing the available bandwidth of some of the communication links, while placing more traffic than a communication link can handle through other communication links, which results in congestion and dropped packets. Further, because packets traveling through different communication links arrive at different times, the packets may arrive at the end node out of sequence. The end node typically uses a large deskewing buffer to store data until all packets have arrived. Then, the end node reassembles the packets in the correct order, which causes additional time delays.
Packet switched networks, may classify the original data into packets, which can be sent through the network via different communication links often out of sequence. Each of the packets is labeled, to allow the destination node to identify and reorder the packets into the original data.
Newer information networks have hardware designed to use packet switching due to its better efficiency. Many existing networks have hardware originally designed for circuit-switching. Several methods have been developed to utilize existing OTNs to efficiently handle packet-switched traffic.
To that end, a need exists for a method and apparatus for transporting high-speed packet flows over an OTN network that provides a more even spread of the packets over multiple circuits than was previously possible with LAGs as constructs in networking solutions, thereby increasing bandwidth utilization and reducing congestion. It is to such an apparatus and method that the inventive concept disclosed herein is directed.